High Speed Packet Access

High Speed Packet Access (HSPA)[1] is an amalgamation of two mobile telephonyprotocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA protocols. A further improved 3GPP standard, Evolved HSPA (also known as HSPA+), was released late in 2008 with subsequent worldwide adoption beginning in 2010. The newer standard allows bit-rates to reach as high as 337 Mbit/s in the downlink and 34 Mbit/s in the uplink. However, these speeds are rarely achieved in practice.[2]

The first HSPA (pronounced “HES-pah”[citation needed]) specifications supported increased peak data rates of up to 14 Mbit/s in the downlink and 5.76 Mbit/s in the uplink. It also reduced latency and provided up to five times more system capacity in the downlink and up to twice as much system capacity in the uplink compared with original WCDMA protocol.

The first step required to upgrade WCDMA to HSPA is to improve the downlink by introducing HSDPA. The improved downlink provides up to 14 Mbit/s with significantly reduced latency. The improvement in speed and latency reduces the cost per bit and enhances support for high-performance packet data applications. HSDPA is based on shared channel transmission and its key features are shared channel and multi-code transmission, higher-order modulation, short transmission time interval (TTI), fast link adaptation and scheduling along with fast hybrid automatic repeat request (HARQ). The upgrade to HSDPA is often just a software update for most WCDMA networks, and as of May 2008 90 percent of WCDMA networks had been upgraded to HSDPA.[3] Voice calls are usually prioritized over data transfer. Singapore's three network providers M1, StarHub and SingTel provide up to 28 Mbit/s throughout the entire island. The Australian provider Telstra provides up to 14.4 Mbit/s nationwide and up to 42Mbit/s in selected areas. The CroatianVIPnet network supports a downlink speed of 7.2 Mbit/s, as does Rogers Wireless in Canada which also supports 21 Mbit/s in the Toronto area.[4] In South Korea, a nationwide 7.2 Mbit/s coverage is now established by SK Telecom and KTF. In Hong Kong, PCCW, CSL and Hutchinson 3 provide 21 Mbit/s coverage and in India BPL, MTS and Tata DoCoMo provide speed of 21.1 Mbit/s nationwide while Reliance ADAE provides speeds up to 28.8 Mbit/s nationwide. Sri Lankan companies like Mobitel, Etisalat provides up to 42 Mbit/s and Dialog, Airtel and Hutch provides 7.2 Mbit/s. In Nepal, HSPA is in a rush. Ncell Currently Provides 42.2 Mbit/s and Nepal Telecom Provides 5.2 Mbit/s. HSPA is Currently replaced by HSPA+ in Nepal.

The second major step in the WCDMA upgrade process is to upgrade the uplink, which is introduced in 3GPP Release 6. Upgrading to HSUPA is usually only a software update. Enhanced Uplink adds a new transport channel to WCDMA, called the Enhanced Dedicated Channel (E-DCH). An enhanced uplink creates opportunities for a number of new applications including VoIP, uploading pictures and sending large e-mail messages. The enhanced uplink increases the data rate (up to 5.8 Mbit/s), the capacity, and also reduces latency. The enhanced uplink features several improvements similar to those of HSDPA, including multi-code transmission, short Transmission Time Interval (TTI), fast scheduling and fast Hybrid Automatic Repeat reQuest (HARQ).

In Singapore, Starhub announced a 1.9 Mbit/s HSUPA Service as part of its new MaxMobile plan on 1 August 2007.[5] In Finland, Elisa announced on 30 August 2007, 1.4 Mbit/s HSUPA to most large cities with plans to add the service to its whole 3G network within months.[6] (The same announcement contained a promise of covering 25% more of Finland by the end of the year, which actually took two more years to accomplish). 3 Italia and Ericsson announced on 16 July 2008, the successful tests of HSUPA 5.8 Mbit/s in the live network of 3 Italia.[7] In Haiti, NATCOM, the former public company now operated by Viettel from Vietnam, offers up to 7.2 Mbit/s nationwide.

Evolved HSPA (also known as HSPA Evolution, HSPA+) is a wireless broadband standard defined in 3GPP release 7 and 8 of the WCDMA specification. It provides extensions to the existing HSPA definitions and is therefore backward-compatible all the way to the original Release 99 WCDMA network releases. Evolved HSPA provides data rates up to 84 Mbit/s in the downlink and 10.8 Mbit/s in the uplink (per 5 MHz carrier) with multiple input, multiple output (2x2 MIMO) technologies and higher order modulation (64 QAM). With Dual Cell technology, these can be doubled.

Since 2011, HSPA+ has been very widely deployed amongst WCDMA operators with nearly 200 commitments.[8]

Dual-Carrier HSDPA (also known as Dual-Cell HSDPA), part of 3GPP Release 8, is the natural evolution of HSPA by allowing a user to connect to two cells at once, thereby theoretically doubling the connection speeds for the user.[9] An HSPA+ network can theoretically support up to 28 Mbit/s and 42 Mbit/s with a single cell, although real speeds are far lower. Besides the throughput gain from doubling the number of cells to be used, some diversity and joint scheduling gains can also be achieved.[10] Dual-cell can particularly improve the QoS (Quality of Service) for end users in poor radio reception where they cannot benefit from the other WCDMA capacity improvements (MIMO and higher order modulations) due to poor radio signal quality. From Release 9 onwards it will be possible to use DC-HSDPA in combination with MIMO. The support of MIMO in combination with DC-HSDPA will allow operators even more capacity improvements within their network.[11]

Similar enhancements as introduced with DC-HSDPA in the downlink for UMTS Release 8 are being standardized for UMTS Release 9 in the uplink, called Dual-Cell HSUPA.[12] applied to HSUPA UL physical channels and DPCCH. The standardisation of Release 9 was completed in December 2009.[13]

The aggregation of more than two carriers has been studied and 3GPP Release 11 is scheduled to include 4-carrier HSPA. The standard is scheduled to be finalised in Q3 2012 and first chipsets supporting MC-HSPA in late 2013. Release 11 specifies 8-carrier HSPA allowed in non-contiguous bands with 4 × 4 MIMO offering peak transfer rates up to 672 Mbit/s.